The overall objectives of the present experiments are to further characterize the chemical composition of canine prostatic fluid and particularly its flow-dependence, to document the changes in its composition produced in response to a number of carefully selected interventions, and finally to arrive at some sound conclusions about the basic or fundamental processes involved in canine prostatic fluid formation. The chemical composition of the fluid is to be characterized by examining fluid being formed at rest (i.e., the basal secretion) and that fluid provoked by electrical stimulation of the hypogastric nerves. The specific parameters to be determined, at least initially, include the concentration of sodium, potassium, chloride, hydrogen (pH), CO2 (pCO2), bicarbonate, total protein and acid phosphatase. The specific interventions to be employed are (1) modification of systemic acid-base balance, (2) drugs known to interfere with electrolyte transport, (3) retrograde injections of mercuric chloride (to selectively destroy ductal cells), (4) stop-flow analysis and (5) elevation of intraluminal pressure (to dissociate water from electrolyte transfer).